Parker is a home rule municipality in Douglas County, Colorado, United States. As a self-declared "Town" under the Home Rule statutes, Parker is the second most populous town in the county; Castle Rock is the most populous. In recent years, Parker has become a commuter town at the southeasternmost corner of the Denver Metropolitan Area. As of the 2010 census the town population was 45,297; the estimated population in 2014 was 49,857. Parker is now the 19th most populous municipality in the state of Colorado.
Parker is located in northeastern Douglas County at 39°31′10″N 104°45′57″W (39.519488, −104.765833). Its northernmost border follows the Arapahoe County line, and the city of Aurora touches the town's northeast border. The center of Parker is 23 miles (37 km) southeast of downtown Denver. Castle Rock, the Douglas County seat, is 15 miles (24 km) to the southwest. Unincorporated communities that border Parker are Dove Valley to the northwest, Stonegate to the west, and The Pinery to the south.